1992 Volume 27 Issue 6 Pages 329-335
In Okutama (Tokyo, Japan), the evaluation of air-polluted environment using the open-top chambers was conducted in 1989-1990. Radish plants (Raphanus sativus L. cv. Comet) were used as the indicator plant for ambient O3.
In the experiments with average daily 8-h (8: 00-46: 00) dose of O3 above 500 ppb·h·day-1 during the exposure period, visible foliar injuries, which were similar to those caused by the exposure to O3, were observed on the cotyledons of the plants cultivated in the non-filtered treatment (NF). In these experiments, leaf areal growth, dry weight growth and net assimilation rate of the plants cultivated in the NF were reduced compared with those of the plants cultivated in the charcoal-filtered treatment (CF). These results suggest that theefficiency of dry matter production of the plants cultivated in the NF was reduced mainly by ambient O3. In the experiments with the dose of O3 below 300 ppb·h·day-1, average daily air temperature below 20°C and average daily cumulative solar radiation below 5 MJ·m-2·day-1, on the other hand, the growth in leaf area and dry weight of the plants cultivated in the NF were increased compared with those of the plants cultivated in the CF.
The results obtained in this survey suggest that O3 has adverse effects on plants mainly in the summer season in Okutama. The OTC-method presented in this paper is useful mainly in the seasons with relatively high air tempez ature and high solar radiation.
